Synthetic polyelectrolytes of varying charge densities but similar molar mass based on acrylamide and their applications on palm oil mill effluent treatment

Cationic polyacrylamides of varying charge densities but similar molar mass were synthesized using free radical polymerization and Mannich reaction, characterized by different methods and applied as flocculants for palm oil mill effluents (POME). Flocculant performance was assessed by determining the polymer dosage, pH of POME and the removal efficiency of the resulting supernatants using turbidity, suspended solids and chemical oxygen demand as indicators. The pH of POME was adjusted to 3 prior to flocculation. It was found that varying the charge density of the polymer from 48.2–485 C/g affects flocculant performance significantly. Polymer adsorption increased as the charge density of the polymers increased. High charge density cationic polyacrylamide (485 C/g) is the most effective polymer as it obtains 98% turbidity removal, 98.7% suspended solids removal and 54% chemical oxygen demand removal with a dosage as low as 32 mg/l at pH 3 of POME.

Based on the above results, the following conclusions can be drawn: • • • • Very low charge density (48.2 C/g) cationic polyacrylamide is effective only at very high dosages up to 250 mg/l. The cationic polyacrylamide with a charge density (161.7 C/g) is also an effective flocculant only at high dosage 200 mg/l to obtain 99% turbidity removal, 99% SS removal and 40% COD removal. By increasing the charge density of cationic polyacrylamide to 355 C/g the removal efficiency will also increase. High charge density cationic polyacrylamide (485 C/g) is the most effective polymer as it obtains a high removal efficiency percentage with a dosage as low as 30 mg/l.